Correlations and Path Analysis in Segregating Cowpea Generations Regarding Biological Nitrogen Fixation

The objective of this research was to evaluate the correlations between variables related to the biological nitrogen fixation (BNF) in segregating generations of cowpea and to unfold these correlations in direct and indirect effects, through path analysis. An outdoor bench experiment was conducted at Carpina Experimental Sugarcane Station of, located at the Zona da Mata region of the State of the Pernambuco, Northeast of Brazil (Federal Rural University of Pernambuco), between March and April 2016. The seeds were planted in 20 cm × 30 cm polyethylene bags, using a substrate composed of a mixture of vermiculite and sand washed in a ratio of 1:1. Bradyrhizobium references, recommended for culture, were used as a mixture of two strains. Parental and F2, F3 and F4 generations were evaluated in a randomized block design with four replicates. Data collection was performed 45 days after the emergency (DAE). Phenotypic correlations and path analysis of the number of nodules per plant (NN), nodules dry mass (NDM), dry roots mass (DRM), dry mass of aerial part (DMAP), nodulation efficiency (NODE) and nitrogen accumulated in the aerial part (NAAP). The phenotypic correlations between the variables related to the BNF showed high magnitudes, demonstrating that there is a great influence of each of the variables on the others, furthermore the path analysis of the coefficients indicated that all the primary components (NN, NDM, DRM, DMAP and NODE) must be considered when it is desired to increase the NAAP in segregating generations of cowpea.

Nitrogen Acquisition Strategies Mediated by Insect Symbionts: A Review of Their Mechanisms, Methodologies, and Case Studies

Nitrogen is usually a restrictive nutrient that affects the growth and development of insects, especially of those living in low nitrogen nutrient niches. In response to the low nitrogen stress, insects have gradually developed symbiont-based stress response strategies—biological nitrogen fixation and nitrogenous waste recycling—to optimize dietary nitrogen intake. Based on the above two patterns, atmospheric nitrogen or nitrogenous waste (e.g., uric acid, urea) is converted into ammonia, which in turn is incorporated into the organism via the glutamine synthetase and glutamate synthase pathways. This review summarized the reaction mechanisms, conventional research methods and the various applications of biological nitrogen fixation and nitrogenous waste recycling strategies. Further, we compared the bio-reaction characteristics and conditions of two strategies, then proposed a model for nitrogen provisioning based on different strategies.

Biochar Enhanced Growth and Biological Nitrogen Fixation of Wild Soybean (Glycine max subsp. soja Siebold & Zucc.) in a Coastal Soil of China

The high salinity and nutrient deficiency in degraded coastal soil restricts crop growth and grain production. The development of effective and novel technology for coastal soil remediation is of great requirement. The effect of wood waste biochar (WB) on the growth and biological nitrogen fixation of wild soybean (Glycine max subsp. soja Siebold & Zucc.), a legume with high economic values and salt tolerance in coastal soil, were explored using a 42-day pot experiment. With the optimal rate of WB addition (1.5%, w/w), the biomass and plant height of wild soybean increased by 55.9% and 28.3%, respectively. WB addition enhanced the photosynthesis (chlorophyll content) and biological nitrogen fixation (nodule number) of the wild soybean. These results may attribute to the improvement of the soil properties including the SOM, NO3−-N content, and WHC. In addition, the shifted bacterial community following WB addition in the coastal soil favored the nitrogen fixation of wild soybean, which was evidenced by the increased abundance of nifH gene and Pseudarthrobacter, Azospirillum, and Rhizobiales. The results of our study suggested the potential of using biochar-based technology to reclaim the coastal degraded soils and enhance the crop growth to ensure food security.

High Genomic Identity between Clinical and Environmental Strains of Herbaspirillum frisingense Suggests Pre-Adaptation to Different Hosts and Intrinsic Resistance to Multiple Drugs

The genus Herbaspirillum is widely studied for its ability to associate with grasses and to perform biological nitrogen fixation. However, the bacteria of the Herbaspirillum genus have frequently been isolated from clinical samples. Understanding the genomic characteristics that allow these bacteria to switch environments and become able to colonize human hosts is essential for monitoring emerging pathogens and predicting outbreaks. In this work, we describe the sequencing, assembly, and annotation of the genome of H. frisingense AU14559 isolated from the sputum of patients with cystic fibrosis, and its comparison with the genomes of the uropathogenic strain VT-16–41 and the environmental strains GSF30, BH-1, IAC152, and SG826. The genes responsible for biological nitrogen fixation were absent from all strains except for GSF30. On the other hand, genes encoding virulence and host interaction factors were mostly shared with environmental strains. We also identified a large set of intrinsic antibiotic resistance genes that were shared across all strains. Unlike other strains, in addition to unique genomic islands, AU14559 has a mutation that renders the biosynthesis of rhamnose and its incorporation into the exopolysaccharide unfeasible. These data suggest that H. frisingense has characteristics that provide it with the metabolic diversity needed to infect and colonize human hosts.